1. Field of the Invention
This invention relates to improvements in automotive clutch disks with elastomer belts for damping torsional shock.
2. Discussion of the Background
U.S. Pat. No. 4,266,409 discloses an energy-absorbing torque transmitter comprising a hub member and a rim member connected by at least one oriented elastomer belt trained over hub and rim rollers. Upon the application of force to either the hub or rim members, the belt is stretched to permit relative rotation of the hub member with respect to the rim member such as to absorb any sudden power surges from the engine while torque is being transferred from one member to the other.
Based on similar principles, a clutch disk has recently been developed in which a hub and a clutch plate are operatively connected by at least two endless elastomer belts, each of the belts being entrained over a pair of bushings one of which is rotatably mounted on a hub pin attached to the hub and the other of which is rotatably mounted on a plate pin attached to the clutch plate. Clutch disks of the type described are advantageous in that the amount of differential rotation permitted between the hub and clutch plate is considerably increased as compared with conventional clutch disks having torsion rubbers or springs due to the fact that the stretching ratio of elastomer belts can be considerably greater than the compression ratio of torsion rubbers or springs.
In clutch disks of this kind, it is important that the bushings be able to rotate smoothly about respective pins. If the smooth rotation of bushings is hindered for any reason, the tension at the two opposite beltruns of elastomer belt becomes unbalanced as the clutch plate displaces angularly with respect to the hub. This causes the belt to slip over the bushings, thereby resulting in unusual wear of the elastomer belt. Furthermore, as the force of sliding friction between the inner surface of the belt and the outer surface of the bushing is not constant, slippage of the elastomer belt causes the torsional hysteresis of the clutch disk to be unstable. To overcome this problem, the earlier developed clutch disk mentioned above employs antifriction bearings such as needle bearings between the bushings and their pins. The provision of antifriction bearings renders the clutch disk structure complex, increases the production costs, and also leads to the problem of bearing lubrication.